​1. Introduction
among individuals with drug abuse disorder is higher than due to direct and indirect harms related to drug abuse. United Nations Office on Drugs and Crime reported that half of the total deaths in the age group15 64 years  can be attributed to drug abuse. Just in the year  2014, 207400 individuals died due to drug abuse disorder worldwide and this number  was 3056 cases in 2012. The scientific evidence shows that individuals with drug abuse disorder live 13.8 years less than the general population. Death among drug abusers occurs due to different reasons such as substance overdose/withdrawal, suicide, and road accidents. In addition, the chances of death due to disease such as HIV/AIDS, hepatitis B and C are much higher among individuals injecting drugs. 
Over the last  two decades, many residential drug treatment centers were established in Iran in order to tackle high demand of drug abuse disorder treatment in cases that there is no indication for outpatient drug addiction treatment, also there are many compulsory residential drug treatment centers. Recently, there some reports such centers.  The Deputy of Prevention and Treatment of Addiction office in the State Welfare Organization reported the occurrence of 39 deaths in residential drug addiction treatment centers just in 2012. As there are no accurate and published reports on mortality rate and cause of deaths in these  centers, the current study aimed at investigating the rate and causes of mortality among those in recovery  in residential addiction treatment centers in Iran.
2. Methods
The current retrospective study was conducted using data of the total mortalities from 2011 to 2016  in all middle and long-term residential addiction treatment centers in Iran using the registry data of these  centers. The data were collected through two questionnaires, the first questionnaire elicited data related to the residential addiction treatment centers and the second questionnaire elicited data related to mortality cases. The questionnaires were designed based on the study, the review of literature, and the existing regulation and guidelines for these  centers.  The questionnaires were sent to the officer in charge of monitoring residential addiction treatment centers in the welfare organizations in 31 provinces and through them to the entire 1141 residential treatment centers around Iran. The residential addiction treatment centers completed questionnaires based on the secondary information in the deceased patients’ reports. The inclusion criteria were all cases of mortality due to any cause even due to accident in residential treatment centers (whether death in residential treatment centers or after transferring from residential addiction treatment centers) in the years 2011 to 2016, in the residential treatment centers. The cases in which mortality occurred one month or more after discharge from residential treatment centers were excluded from the study. The data were collected during three months from May to September 2017. Data analysis was performed using for the Social Sciences (SPSS) software  version 19 and using descriptive data as frequency and percentage, mean, and standard deviation. 
3. Results
Totally, data were collected from 25 out of 31 provinces and 371 centers. Overall, during the five years of the study period (2011-2016), 107 people died in the residential addiction treatment centers. The highest mortality rates were in Tehran (14.0%), East Azarbaijan (11.2%), and Kerman (7.5%), respectively The proportion of deaths among the subjects sentenced to residential treatment centers under (47 per 100000 individuals) was higher than the ratio of deaths among the subjects voluntarily referred to residential addiction treatment centers (21 per 100000 individuals). The average time gap  between admission to residential addiction treatment centers and occurrence of death was 11 days and at least half of the cases died during the first five days of admission to the residential treatment centers. The number of deaths increased from 2011 to 2016 in residential treatment centers. 
The data related to mortality information was available for 107 cases. Totally, 91.6% of cases were male and the majority of them (78.3%) had not finished high school More than half of the cases (50.5%) were married and 73.8% were unemployed. Nearly one fifth of subjects (17.5%) were homeless.  The mean age of the cases was 39 years at the time of death and most of the mortality cases occurred in the age group of 21 to 35 years. Substance overdose/withdrawal and cardiovascular disease were reported as the most important causes of deaths. Heroin (27.3%), crystal (21.8%), methadone (13.8%), and opium (14.5%) the main drug of abuse. Medical screening was reported for 76.9% of cases at the admission time. No physical health problems were in nearly two-thirds of the cases (70.4%), and no mental problems history in 91.1%.

4. Discussion
The result of the current study showed that among mandatory residential of treatment centers under was 13 times more than the total mortality rate among the ones referred to residential treatment centers, which could be due to of the centers compared to that of the treatment centers. Also, the current study showed that the total number of deaths increased by eight times during the previous five years. The study findings showed that 91.6% of deaths occurred among males that could be due to population of male subjects among the target group and lack of enough female residential treatment centers in Iran. The average age of death was 39 years, which was 30 years below the life expectancy in Iran (74.77 years). 
According to the current study, the two main causes of death were cardiovascular disease and substance overdose. Cardiovascular related death can occur as a result of withdrawal from drugs without medical supervision and substance overdose usually occurs when these patients swallow a large amount of drugs to hide them from the police at the time of arrest or to use them later in these  centers. The finding that the average time of death was 11 days after registration and half of the cases occurred in the first five days showed that the mortality in residential treatment centers occurred during therefore medically supervised detoxification should be done  in all these  centers. Although the results of the current study cannot be generalized to the whole country due to under reporting,   the current study showed that the total number of deaths in residential addiction treatment centers increased during 2011 to 2016  and mortality rates of the subjects referred to residential addiction treatment centers were high; most of these deaths could be prevented with timely and effective measures.
Ethical Considerations
Compliance with ethical guidelines
As this study used anonymous secondary data, there is no need for code of ethical guideline.
Funding
Iran University of Medical Science financially supported this study.



Conceptualization, methodology: all authors; Investigation: Mohsen Roshanpajouh, Roksana Mirkazemi, Hassan Asadi; Writing: Roksana Mirkazemi, Bita Hedayati; Review and editing: Mohsen Roshanpajouh, Hassan Asadi; Funding acquisition: Mohsen Roshanpajouh; Supervision: Mohsen Roshanpajouh, Roksana Mirkazemi.
Conflict of interest
The authors no conflict of interests.
Acknowledgements
the State Welfare Organization for their help in data collection and also all the residential addiction treatment centers for providing